Previously they appeared centered at the top of the page;
now we put them centered at the bottom, unless the `pagenumbering`
variable is set (this gives users full control over page
number format and position,
https://wiki.contextgarden.net/Command/setuppagenumbering)
* Let the user choose type of PDF/A generated with ConTeXt (closes#5608)
* Updated ConTeXt test documents for changes in tagging
* Updated color profile settings in accordance with ConTeXt wiki
* Made ICC profile and output intent for PDF/A customizable
* Read pdfa variable from meta (and updated manual)
Fixes#2609.
This PR introduces the new-style section headings: `\section[my-header]{My Header}` -> `\section[title={My Header},reference={my-header}]`.
On top of this, the ConTeXt writer now supports the `--section-divs` option to write sections in the fenced style, with `\startsection` and `\stopsection`.
